The invention relates to gaseous-based detectors for detection of ionizing radiation and to apparatus for radiography.
Gaseous-based ionizing radiation detectors, in general, are very attractive since they are cheap to manufacture, and since they can employ gas multiplication to strongly amplify the signal amplitudes.
A typical gaseous-based ionizing radiation detector comprises a planar cathode and anode arrangement, respectively, and an ionizable gas arranged between the cathode and anode arrangements. The detector is arranged such that a radiation beam from a radiation source can enter the detector for ionizing the ionizable gas. Further, a voltage is typically applied for drifting electrons created during ionization of the ionizable gas towards the anode. The voltage and the design of the detector electrodes may be adjusted such that multiplication of electrons is achieved to induce an amplified charge at the anode arrangement. A readout arrangement, which typically includes a plurality of readout elements, is arranged adjacent the anode arrangement for detecting the electrons drifted towards the anode arrangement.
A particular kind of gaseous detector is the one, in which electrons released by interactions between photons and gas atoms can be extracted in a direction essentially perpendicular to the incident radiation. Hereby, an improved spatial resolution is obtained.
However, in all kind of gaseous-based ionizing radiation detectors spark discharges can occur in the gas due to the strong electric fields created in the detector. Such events are particularly probable to occur in high amplification detectors.
The spark discharges block the detector for a period of time, and can also be harmful for the detector and particularly for electronics thereof.
A main object of the invention is to provide a detector for detection of ionizing radiation wherein problems caused by spark discharges are eliminated, or at least reduced.
In this respect a particular object of the invention is to provide such detector wherein the energy in any occurring sparks is low such that relatively few charges are released in the gas.
A further object of the present invention is to provide such detector, which provides for fast recovery subsequent to a spark discharge, and thus provides for faster detection and shorter time periods during which an object under investigation is exposed for ionizing radiation.
Yet a further object of the invention is to provide such detector, which is effective, accurate, and of low cost.
Still a further object of the invention is to provide such detector, which is reliable and has a long lifetime.
In this respect there is a particular object of the invention to provide such detector, which protects the anode and readout electronics such as e.g. preamplifiers from being damaged by high energy sparks.
Yet a further object of the invention is to provide an apparatus for planar beam radiography, comprising a detector for detection of ionizing radiation, which limits the problems caused by spark discharges.
Such objects, among others, are attained by radiation detectors and apparatus for planar beam radiography as claimed in the appended claims.